Sharing your side project and intentions with your employer satisfies "right of first refusal", which will become much more valuable to have brought up formally

Sharing your side project and intentions with your employer satisfies "right of first refusal", which will become much more valuable to have brought up formally on the offchance emplyers attempt to sue for ownership. Also, this formalizes standing on both sides; both parties will know more clearly where each stands. Of course you may proceed without sharing, but might also end up losing more later. Calculated risk.